Decimal Sum Dilly-Dallying
Level
pending
Let f(n) denote the digit sum of integer n when written in decimal notation. What is fff(4444^4444)?
The answer is 7.
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1 solution
Assuming fff(n) is f(f(f(n))), then you have to find the digit sum three times.
The digit sum of 4 4 4 4 4 4 4 4 is 7 2 6 1 0 ,
The digit sum of 7 2 6 1 0 is 1 6 ,
The digit sum of 1 6 is 7 .
The answer is 7 .